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Re: VACUUM and spoiling the buffer manager cache

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: VACUUM and spoiling the buffer manager cache
Date: 2007-03-01 09:09:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Thu, 2007-03-01 at 11:00 +0900, ITAGAKI Takahiro wrote:
> "Simon Riggs" <simon(at)2ndquadrant(dot)com> wrote:
> > > > VACUUM's current behaviour is to take blocks it has touched and place
> > > > them on the head of the freelist, allowing them to be reused.
> > > 
> > > No, it puts them at the tail of the freelist.
> > 
> > That's a minor point because the freelist is mostly empty, so head ==
> > tail in 99.9% of cases.
> That's correct. Also, even if a VACUUM process collects some unused buffers
> into the freelist, other backends comsume all of them in a moment.

AFAICS the patch is useful and valid. 

Please could we have some additional testers, so that we have a range of
opinion, rather than just my/EDB tests.

I'll submit further detailed tests after feature freeze, since right now
I have other things to do, but I'll return to this point again.

  Simon Riggs             

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